Hi, I've been having trouble getting my van to run happily when cold - whether it's on or off choke and it's just not drivable. It seems to take a long time to warm the engine up until it's finally running smooth (20 minutes, sometimes longer to burn the plugs clean, read below). Is this normal?

It's a 360 with a Uremco reconditioned 2 barrel holley 2245. EGR systems deleted. Has an RPV / original pan filter and snorkel.

When warmed up, the van runs smooth and idles ok etc.

With the choke hooked up and calibrated as manual specs, the van smokes very rich black smog on the drivers side. It maybe fast idles for a moment before the engine starts loading and coking up the idle speed slows and stumbles and it runs like crap - the plugs foul and it runs terribly until fully warmed or until I pull the plugs and clean them up or go for a long, high rpm, light-throttle drive on the highway to burn the plugs clean.

I have a good understanding of how the divorced choke, vac pull-off and idlecams work together and I have been trying to tune it starting from manual specs to cure the conditions / symptoms below.

I have tried cold starting with the divorced choke disconnected. The van still runs terribly for a long time until warm (a good 20 minutes) and is not practical nursing the throttle at junctions and traffic lights.
When driving cold, the engine feels stifled, is hesitant, stumbling and spitting and popping and feels like it's not firing fully on all cylinders. (fouled plugs!)

So I figured the van hates being choked but would like a high fast idle speed. It will load up and foul the plugs and be eye-stinging rich. (idle circuits are happiest tuned at just half a turn out - lean!).

I feel like the van would benefit from the choke system being set up for a high fast idle speed (crack the butterfly open to get some RPMs and heat in the block fast!) BUT also have minimal choking (choke flap kicked at least half open with vac pull-off / or the old drill a hole in the choke flap trick?).

I know the choke systems are linked (choke flap and idle cam are linked) so I'm having trouble tuning the choke how I think it wants it (lots of idle speed, air, and minimal choke). Any ideas?


Other thoughts:

Another option would be to get a manual choke kit - anyone know if these exist for a holley 2245?

Currently has an orange FRAM air filter (these any good?) in the original pan with snorkel and hot air feed from rocker cover. Maybe I could get it breathing better with a K&N filter? Van seems to do better when I have the air filter off when im tuning it and driving / diagnosing it / inspecting the choke as it warms.

Bonus thought: I recently found the van has a heat riser valve in the passenger exhaust header which is supposed to open as the engine warms up via thermospring. Which sends exhaust gas through the exhaust crossover in the intake to warm it and out the driver's side header. That explains the rich black smoke on the drivers side!
The valve is freely turning and returns closed with the spring when cold - but doesn't seem to stay fully open when hot (also tried heating with blow torch). When I throttle the engine the flap bounces clockwise to about half open and returns to rest only about 1/4 open) Doesn't seem to be working properly... although I have read it may only fully open with exhaust pressure - hence it bouncing open and back and forth when throttling). Today I wired the valve open to see if it would help the smog and warm up. Exhuasts sounded louder, cold start was still terrible, seemed to balance out the smog side-to-side on the exhaust pipes. Temps ran cooler. Ran all day at 160*. When it usually runs 180*. Might put this back to help warm the engine quicker. Edit: the operation of this sounds correct and ok. Probably the crossover channel is blocked. https://www.hemmings.com/stories/article/all-rise

Thanks for reading. I look forward to reading your ideas. Sensible and intelligible only please.


I'm frustrated because I have a small block chevy gasser that fires straight up cold with no choke and I can manually nurse the throttle for 1 minute before it's running sweet and I can drive it off right away no problems. However that is super simple hot rod engine set up, open headers, 4 brrl, no emissions BS. These vans seem to have so many crazy emissions systems going on I'm discovering a new one every five minutes. I'm tempted to throw a new intake, 4 barrel carb and headers on it.

I had a similar problem on a 78 Chrysler, the manifold was plugged with carbon, looked like a piece of charcoal when I chiseled it out. Can't remember the correct term for the part that was plugged, but I believe it had something to do with the choke. The car would run crappy till warmed-up. How I found out it was plugged, a guy at a carburetor shop told me to start the car and keep my hand on the top of the intake manifold, if I could hold my hand there more than a couple minutes without it getting hot, the manifold was plugged, and he was correct. Does your van have the Lean-Burn system on the carburetor.

Hi, thanks. Don't think the carb has any lean burn systems. Standard carb with no additional vac or electronics here. Have a look at the photo?

I have been reading that the exhaust cross over passages in the intakes can get clogged with soot. Makes sense that could happen with that the heat riser valve sending smog back across the inlet from the passenger side and out the drivers header. I will feel the inlet with my hands (I lost my laser thermometer pointer). And maybe that's why the choke is staying on too long and blacking the plugs. Divorced choke relying on the intake to warm quickly. Thing is, if I'm having the intake off for a clean, I'll need a new gasket and screws kit etc. At that point I'll be very tempted to fit a aftermarket intake.

Do you think I could clean it up manually? Chiselling you say... 😬. Could remove and soak in petrol?

Interesting...

I've been doing some reading and trying to get my head around it..

The exhaust crossover passage on intake is likely blocked with years of carbon. Makes sense, because the thermostat looked like it had been at the bottom of the sea for 50 years. Cold intake = fuel puddles rather than amotmises in the plenum = runs rich until warm. Also because of divorced choke being set into the intake condition is worsened, richer mix for longer as the choke is staying on longer and fouling the plugs, sometimes making it run like crap even after its warmed up, until I brush up or burn the plugs clean.

Solutions...
Clean and unblock the exhaust crossover passage?
Or fit new intake?
Fit an electric or manual choke?

If you used one of those 'fail safe' thermostats, they can get locked open from heat soak after the engine is shut off. They sound like a great idea. marketing is effective...

Take the radiator cap off when cold and start the engine. if coolant starts flowing past instantly the opening at a good pace the thermostat is likely stuck open.

I've got some K type thermocouples attached to radiator upper hose and to thermostat housing body. It usually takes about 1 mile of driving mildly before the thermostat starts opening and radiator temps start climbing.

If shutting off the engine right after a long freeway drive, the thermocpouple on my T stat housing rises to 220f from the 196.5f max I usually see, unless climbing grades but then max is around 205.5f.

Mines an '89 with TBI, and one time I used a 185f tstat instead of the 195f that the engine computer was expecting, and mpgs took a dump until I replaced it with a 195f.

I've used some hose clamps to hold my passenger side diverter valve wide open. I am usually in mild climates and find the crossover unnecessary, and have to pass California smog tests every 2 years and no smog tech has ever said anything about this emissions component being visibly disabled.

I can tell it runs a bit crustier when cold when the heat riser tube is not properly attached/ missing and is not sucking warmer air from around E manifold on warm up, but it is not a huge difference.

The laser pointer on IR temp guns, does not use the laser dot to measure temps. When aimed at reflective surfaces like aluminum, they often read much lower than actual.

K type thermocouples often come with digital multimeters, You might already have one. You could tape it tightly to the base of the carb.

Great idea to check the thermostat. Thanks bud.

So I've just been out in the van and she was alright. I think've been over-thinking and over-complicating things as usual. I've set the choke in a unique way so that the choke flap opens when the engine starts but remains on a fast idle cam. But I need to follow this starting procedure. I didn't yesterday, I accidentally pumped the throttle (dry float bowl after sitting) as it was cranking which kicked the choke off fast idle.

When cold the choke flap is fully closed and is on the third fast idle cam step.

I need to crank the engine to fill the carb fuel bowl. Pump a couple squirts from the accelrator pump and set the choke flap closed. Then very important... leave the pedal alone.

Once the engine starts I have the vacum-break linkage tuned to completely open the choke flap. At this point I NEED TO LEAVE THE THROTTLE ALONE and leave it fast idling on the third cam with an open choke flap for a minute and smoke a cigarette, open the bat cave doors etc.
This is getting lots of heat into the intake - I can feel it is getting hot fast on the left and right under the carb where the EGR valve and divorced choke are mounted. The rest of the intake (air/fuel passages) are cool - perfect! There is no lumpy idling or chugging or insanely rich eye-stinging smoke when the van is idling fast like this.

As soon as I touch the throttle, the choke steps down onto the second step on the fast idle cam and I am able to drive with a fast idle and a drivable responsiveness (still bit fluffy over half throttle).

After about 10 minutes of mixed driving and idling the choke is starting to fully disenage and droppping onto the curb idle cam position and it'll have a smooth curb idle speed.

Basically I've tuned the choke so that it is utlising the fast idle cam but not closing the choke flap.
Because just hates being choked, and the carb idle mixture likes being set lean. Only thing I can think of with all the original california emissions equipment removed it's running rich.

I kept the heat riser valve wired open too. Didn't seem to effect the warming of the intake too much and seems to helped with reducing the smog. It is mild today (40*f).

Had the cap off the rad too when engine running and I didn't get covered in coolant - so assuming the stat is closed and not stuck open.

I still feel like the air filter might be restrictive. The carb really sucks a lot of air to fill up those 6 litres of cyclinders! Runs great with the hat off, maybe I should get a less restrictive air filter green / k&n any good ? or same as standard fram part?

Hi Moog, Welcome to the Site! I used to run a K and N when I drove 1000 miles plus a week. As to flow, your 360 won't care one way or the other. If you have drivability issues, check your exhaust. It could be restricted. Motors don't like that. Vacuum leaks either. Good Hunting Mate!

Thanks bud, I've been round checking vac leaks. As that's first place to start for me. It has got relatively new cherry bombs with about 300 miles on, so potentially they could do with a run in and blowing some glass out.

I threw out my K&N air filter after finding a fine layer of dust in throttle body and holding the filter upto sunlight and seeing right through it. The typical online responses from K&N fanboys were I under or over maintained it.

The carb throat is going to add more restriction to flow than a paper filter element ever could, until it's nearly totally clogged.

Better to add a cold air intake of not already present. IIRC wedgy beefed his up. I've been thinking about doing the same but mostly as my stock accordian plastic CAI pipe is cracked in places and was allowing some prewarmed air to enter. For now I just used some Nashua Flexfix tape to seal those cracks.

A new set of spark plugs sorted it.

Any reason why my number 2 cylinder spark plug is black and the rest are white?

Turns out the problem I was having was from a split carb to manifold gasket.

Even though I had tried the usual spraying gt40 / wd around the carb base to check for vac leaks and found no change in rpm.

When I tweaked / pulled the carb up slightly the engine would stumble and die.

The carb gasket actually looked ok, was just a bit delaminated.

After fitting a new gasket she's running great now. Very happy.


Very rich exhaust condition caused by a lean mixture. WHO KNEW. Livin' and learnin'